Lens Form: Sphere, Cylinder, and Axis

It can be helpful to think of very basic lens forms in terms of prisms. Recall, as light passes through a prism it is refracted toward the prism base. Minus lenses therefore resemble two prisms apex to apex spreading light rays outward as they pass through the lens,...

Boxing System

In 1962 the Optical Manufacturers Association adopted the boxing system to provide a standard for frame and lens measurement that greatly improved upon the accuracy of previous systems. The boxing system is based upon the idea of drawing an imaginary box around a lens...

Transposing Prescriptions

Depending on the equipment used by the doctor, a prescription may be in plus or minus cylinder form. For surfacing, the lab uses the minus form, meaning if a prescription is written in a plus cylinder form it must be transposed before processing. Transpose a...

Prism

Prism can be used to correct vision for an individual whose eyes are not perfectly aligned as with, for example, a patient with strabismus. When the eyes are not aligned, the right and left eye see different images resulting in blurred or double vision. Sometimes the...

Prism by Decentration

Normally, eyeglasses are fitted with the optical center of the lens directly in front of the eye. If the lens is fit off-center, image displacement can occur due to induced prism. The higher the power or the further the lens is fit off-center, the higher is the...

Don't Miss Out!

Join Over 10,000 Other Optical Professionals. Become the best optician you can be with weekly content; tips, stories, and science to help you focus on getting the most from your optical business and career delivered to your inbox.

You have Successfully Subscribed!